1. Field of the Invention
The present invention is directed to diagnostic equipment and, more particularly, to diagnostic equipment of the type used to measure range of motion of human joints.
2. Description of the Invention Background
Bio-mechanical research into the intricacies of human body joint movement and the need for a more intuitive approach to man-machine interface requirements are pushing the capabilities of current joint measurement technology. A majority of the human-body joints are multi-axis, rotational hinges. The motion of such multi-axis joints is difficult to accurately track and report. Multi-axis human body joints, such as the wrist, can perform complex movements during the execution of even simple tasks such as tying a knot in a shoestring or turning a door knob. It is critical that the joint measuring apparatus accurately track and report the movements of each axis of the joint. Bio-mechanical research into tendon excursions and repetitive motion injuries depend upon accurate and distinct sensing of each axis.
Alignment of a sensor's axis to a joint's rotation axis is critical to accurately tracking the motion of the joint. What is subtle, and frequently overlooked by technicians in this field, is that the sensor's axis must not only be aligned to the axis that it is sensing, but it also must be aligned with respect to the axis that is not being sensed. That is, a sensor measuring an axis designated as axis 1, must also be aligned to axis 2 in a two axis joint. Alignment of the sensor with respect to axis 2 is required so that movement with respect to axis 2 is not tracked by the sensor. Assuming that the sensor is designed so that it has a well defined sense axis that will not respond to movements orthogonal to that sense axis, off-axis tracking can be eliminated by positioning the sensor responsive to axis 1 orthogonal to axis 2. The sensors described in U.S. Pat. No. 5,316,017 are such sensors.
Physically adjusting the positions of the sensors on, for example, a data glove to eliminate the tracking of off-axis movement is very difficult. Each time a patient dons the data glove, even minute differences in the position of the glove can result in the sensors being positioned in less than the optimal position. The problem is exacerbated further when the same data glove is worn by patients whose body parts may be of different size or disfigured due to accident or illness. A data glove having sensors precisely aligned for one patient, will necessarily require realignment of the sensors for another patient.
Mechanical realignment of the sensors to eliminate tracking of off-axis movement can be tedious, difficult to accomplish and maintain, and, if performed improperly, lead to erroneous results. Accordingly, a method and apparatus for permitting precise alignment of sensors carried by a data glove or other garment so that off-axis movement is not tracked is desirable.